JP8-45521A published by the Japanese Patent Office in 1996 and JP11-307110A published by the Japanese Patent Office in 1999 disclose a fuel cell system wherein raw fuel having hydrocarbons as its main component is vaporized, and the raw material vapor and air are supplied to a reformer. In the reformer, hydrocarbons in the raw material and oxygen in the air react together to produce hydrogen-rich reformate gas. The hydrogen-rich reformate gas and air are supplied to the fuel cell, and in the fuel cell, the hydrogen in the reformate gas and oxygen in the air undergo an electrochemical reaction to produce power.